Fast and Reversible Li Ion Insertion in Carbon‐Encapsulated Li3VO4 as Anode for Lithium‐Ion Battery

Carbon‐encapsulated Li₃VO₄ is synthesized by a facile environmentally benign solid‐state method with organic metallic precursor VO(C₅H₇O₂)₂ being chosen as both V and carbon sources yielding a core–shell nanostructure with lithium introduced in the subsequent annealing process. The Li₃VO₄ encapsulated with carbon presents exceeding rate capability (a reversible capability of 450, 340, 169, and 106 mAh g^?1 at 0.1 C, 10 C, 50 C, and 80 C, respectively) and long cyclic performance (80% capacity retention after 2000 cycles at 10 C) as an anode in lithium‐ion batteries. The superior performance is derived from the structural features of the carbon‐encapsulated Li₃VO₄ composite with oxygen vacancies in Li₃VO₄, which increase surface energy and could possibly serve as a nucleation center, thus facilitating phase transitions. The in situ generated carbon shell not only facilitates electron transport, but also suppresses Li₃VO₄ particle growth during the calcination process. The encouraging results demonstrate the significant potential of carbon encapsulated Li₃VO₄ for high power batteries. In addition, the simple generic synthesis method is applicable to the fabrication of a variety of electrode materials for batteries and supercapacitors with unique core–shell structure with mesoporous carbon shell.     

Carbon‐Nanotube‐Cored Cobalt Porphyrin as a 1D Nanohybrid Strategy for High‐Performance Lithium‐Ion Battery Anodes

Redox‐active organic electrode materials have garnered considerable interest as an emerging alternative to currently widespread inorganic‐(or metal)‐based counterparts in lithium‐ion batteries (LIBs). Practical use of these materials, however, has posed a challenge due to their electrically insulating nature, limited specific capacity, and poor electrochemical durability. Here, a new class of multiwalled‐carbon‐nanotube‐(MWCNT)‐cored, meso‐tetrakis(4‐carboxyphenyl)porphyrinato cobalt (CoTCPP) is demonstrated as a 1D nanohybrid (denoted as CC‐nanohybrid) strategy to develop an advanced LIB anode. CoTCPP, which is one of the metalloporphyrins having multielectron redox activities, shows strong noncovalent interactions with MWCNTs due to its conjugated π‐bonds, resulting in successful formation of the CC‐nanohybrids. The structural uniqueness of the CC‐nanohybrid facilitates electron transport and electrolyte accessibility, thereby improving their redox kinetics. Inspired by the 1D structure of the CC‐nanohybrid, all‐fibrous nanomat anode sheets are fabricated through concurrent electrospraying/electrospinning processes. The resulting nanomat anode sheets, driven by their 3D bicontinuous ion/electron conduction pathways, provide fast lithiation/delithiation kinetics, eventually realizing the well‐distinguishable lithiation behavior of CoTCPP. Notably, the nanomat anode sheets exhibit exceptional electrochemical performance (≈226 mAh g_sheet ^?1 and >1500 cycles at 5 C) and mechanical flexibility that lie far beyond those achievable with conventional LIB anode technologies.     

Strain Anisotropies and Self‐Limiting Capacities in Single‐Crystalline 3D Silicon Microstructures: Models for High Energy Density Lithium‐Ion Battery Anodes

This study examines the crystallographic anisotropy of strain evolution in model, single‐crystalline silicon anode microstructures on electrochemical intercalation of lithium atoms. The 3D hierarchically patterned single‐ crystalline silicon microstructures used as model anodes were prepared using combined methods of photolithography and anisotropic dry and wet chemical etching. Silicon anodes, which possesses theoretically ten times the energy density by weight compared to conventional carbon anodes, reveal highly anisotropic but more importantly, variably recoverable crystallographic strains during cycling. Model strain‐limiting silicon anode architectures that mitigate these impacts are highlighted. By selecting a specific design for the silicon anode microstructure, and exploiting the crystallographic anisotropy of strain evolution upon lithium intercalation to control the direction of volumetric expansion, the volume available for expansion and thus the charging capacity of these structures can be broadly varied. We highlight exemplary design rules for this self‐strain‐limited charging in which an anode can be variably optimized between capacity and stability. Strain‐limited capacities ranging from 677 mAhg^?1 to 2833 mAhg^?1 were achieved by constraining the area available for volumetric expansion via the design rules of the microstructures.     

Nanostructured Silicon Anodes for High‐Performance Lithium‐Ion Batteries

Despite the high theoretical capacity of Si anodes, the electrochemical performance of Si anodes is hampered by severe volume changes during lithiation and delithiation, leading to poor cyclability and eventual electrode failure. Nanostructured silicon and its nanocomposite electrodes could overcome this problem holding back the deployment of Si anodes in lithium‐ion batteries (LIBs) by providing facile strain relaxation, short lithium diffusion distances, enhanced mass transport, and effective electrical contact. Here, the recent progress in nanostructured Si‐based anode materials such as nanoparticles, nanotubes, nanowires, porous Si, and their respective composite materials and fabrication processes in the application of LIBs have been reviewed. The ability of nanostructured Si materials in addressing the above mentioned challenges have been highlighted. Future research directions in the field of nanostructured Si anode materials for LIBs are summarized.     

Tungsten‐Based Materials for Lithium‐Ion Batteries

Lithium‐ion batteries are widely used as reliable electrochemical energy storage devices due to their high energy density and excellent cycling performance. The search for anode materials with excellent electrochemical performances remains critical to the further development of lithium‐ion batteries. Tungsten‐based materials are receiving considerable attention as promising anode materials for lithium‐ion batteries owing to their high intrinsic density and rich framework diversity. This review describes the advances of exploratory research on tungsten‐based materials (tungsten oxide, tungsten sulfide, tungsten diselenide, and their composites) in lithium‐ion batteries, including synthesis methods, microstructures, and electrochemical performance. Some personal prospects for the further development of this field are also proposed.     

Magnesium Anodes with Extended Cycling Stability for Lithium‐Ion Batteries

Magnesium as a promising alloy‐type anode material for lithium‐ion batteries features both high theoretical specific capacity (2150 mAh g^?1) and stack energy density (1032 Wh L^?1). However, the poor cycling performance of Mg‐based anodes severely limits their application, mainly because high‐impedance films can grow easily on the surface of Mg and cause diminished electrochemical activity. As a result, the capacities of reported Mg anodes fade quickly in less than 100 cycles. To improve the stability of Mg anodes, 3D Cu@Mg@C structures are prepared by depositing Mg/C composite on 3D Cu current collectors. The resulting 3D Cu@Mg@C anodes can deliver an initial capacity of 1392 mAh g^?1. With a second‐cycle capacity of 1255 mAh g^?1, 91% can be retained after 1000 cycles at 0.5 C. When cycled at 2 C, the initial capacity can be maintained for 4000 cycles. This remarkably improved cycling performance can be attributed to both the 3D structure and the embedded carbon layers of the 3D Cu@Mg@C electrodes that facilitate electrical contact and prevent the growth of high‐impedance films during cycling. With 3D Cu@Mg@C anodes and LiFePO₄ cathodes, full cells are assembled and charging by a rotating triboelectric nanogenerator that can harvest mechanical energy is demonstrated.     

Ultrathin‐Nanosheet‐Induced Synthesis of 3D Transition Metal Oxides Networks for Lithium Ion Battery Anodes

A general ultrathin‐nanosheet‐induced strategy for producing a 3D mesoporous network of Co₃O₄ is reported. The fabrication process introduces a 3D N‐doped carbon network to adsorb metal cobalt ions via dipping process. Then, this carbon matrix serves as the sacrificed template, whose N‐doping effect and ultrathin nanosheet features play critical roles for controlling the formation of Co₃O₄ networks. The obtained material exhibits a 3D interconnected architecture with large specific surface area and abundant mesopores, which is constructed by nanoparticles. Merited by the optimized structure in three length scales of nanoparticles–mesopores–networks, this Co₃O₄ nanostructure possesses superior performance as a LIB anode: high capacity (1033 mAh g^?1 at 0.1 A g^?1) and long‐life stability (700 cycles at 5 A g^?1). Moreover, this strategy is verified to be effective for producing other transition metal oxides, including Fe₂O₃, ZnO, Mn₃O₄, NiCo₂O₄, and CoFe₂O₄.     

Making Ultrafast High‐Capacity Anodes for Lithium‐Ion Batteries via Antimony Doping of Nanosized Tin Oxide/Graphene Composites

Tin oxide‐based materials attract increasing attention as anodes in lithium‐ion batteries due to their high theoretical capacity, low cost, and high abundance. Composites of such materials with a carbonaceous matrix such as graphene are particularly promising, as they can overcome the limitations of the individual materials. The fabrication of antimony‐doped tin oxide (ATO)/graphene hybrid nanocomposites is described with high reversible capacity and superior rate performance using a microwave assisted in situ synthesis in tert‐butyl alcohol. This reaction enables the growth of ultrasmall ATO nanoparticles with sizes below 3 nm on the surface of graphene, providing a composite anode material with a high electric conductivity and high structural stability. Antimony doping results in greatly increased lithium insertion rates of this conversion‐type anode and an improved cycling stability, presumably due to the increased electrical conductivity. The uniform composites feature gravimetric capacity of 1226 mAh g^?1 at the charging rate 1C and still a high capacity of 577 mAh g^?1 at very high charging rates of up to 60C, as compared to 93 mAh g^?1 at 60C for the undoped composite synthesized in a similar way. At the same time, the antimony‐doped anodes demonstrate excellent stability with a capacity retention of 77% after 1000 cycles.     

Simple Synthesis of Hollow Tin Dioxide Microspheres and Their Application to Lithium‐Ion Battery Anodes

Hollow tin dioxide (SnO₂) microspheres were synthesized by the simple heat treatment of a mixture composed of tin(IV ) tetrachloride pentahydrate (SnCl₄·5H₂O) and resorcinol–formaldehyde gel (RF gel). Because hollow structures were formed during the heat treatment, the pre‐formation of template and the adsorption of target precursor on template are unnecessary in the current method, leading to simplified synthetic procedures and facilitating mass production. Field‐emission scanning electron microscopy (FE‐SEM) images showed 1.7–2.5 μm sized hollow spherical particles. Transmission electron microscopy (TEM) images showed that the produced spherical particles are composed of a hollow inner cavity and thin outer shell. When the hollow SnO₂ microspheres were used as a lithium‐battery anode, they exhibited extraordinarily high discharge capacities and coulombic efficiency. The reported synthetic procedure is straightforward and inexpensive, and consequently can be readily adopted to produce large quantities of hollow SnO₂ microspheres. This straightforward approach can be extended for the synthesis of other hollow microspheres including those obtained from ZrO₂ and ZrO₂/CeO₂ solid solutions.     

Toward High Performance Thiophene‐Containing Conjugated Microporous Polymer Anodes for Lithium‐Ion Batteries through Structure Design

Poly(thiophene) as a kind of n‐doped conjugated polymer with reversible redox behavior can be employed as anode material for lithium‐ion batteries (LIBs). However, the low redox activity and poor rate performance for the poly(thiophene)‐based anodes limit its further development. Herein, a structure‐design strategy is reported for thiophene‐containing conjugated microporous polymers (CMPs) with extraordinary electrochemical performance as anode materials in LIBs. The comparative study on the electrochemical performance of the structure‐designed thiophene‐containing CMPs reveals that high redox‐active thiophene content, highly crosslinked porous structure, and improved surface area play significant roles for enhancing electrochemical performances of the resulting CMPs. The all‐thiophene‐based polymer of poly(3,3′‐bithiophene) with crosslinked structure and a high surface area of 696 m² g^?1 exhibits a discharge capacity of as high as 1215 mAh g^?1 at 45 mA g^?1, excellent rate capability, and outstanding cycling stability with a capacity retention of 663 mAh g^?1 at 500 mA g^?1 after 1000 cycles. The structure–performance relationships revealed in this work offer a fundamental understanding in the rational design of CMPs anode materials for high performance LIBs.     

A Robust Ion‐Conductive Biopolymer as a Binder for Si Anodes of Lithium‐Ion Batteries

Binders have been reported to play a key role in improving the cycle performance of Si anode materials of lithium‐ion batteries. In this study, the biopolymer guar gum (GG) is applied as the binder for a silicon nano­particle (SiNP) anode of a lithium‐ion battery for the first time. Due to the large number of polar hydroxyl groups in the GG molecule, a robust interaction between the GG binder and the SiNPs is achieved, resulting in a stable Si anode during cycling. More specifically, the GG binder can effectively transfer lithium ions to the Si surface, similarly to polyethylene oxide solid electrolytes. When GG is used as a binder, the SiNP anode can deliver an initial discharge capacity as high as 3364 mAh g^?1, with a Coulombic efficiency of 88.3% at the current density of 2100 mA g^?1, and maintain a capacity of 1561 mAh g^?1 after 300 cycles. The study shows that the electrochemical performance of the SiNP anode with GG binder is significantly improved compared to that of a SiNP anode with a sodium alginate binder, and it demonstrates that GG is a promising binder for Si anodes of lithium‐ion batteries.     

SiO2/TiO2 Composite Film for High Capacity and Excellent Cycling Stability in Lithium‐Ion Battery Anodes

In this study, partially crystalline anodic TiO₂ with SiO₂ well‐distributed througout the entire oxide film is prepared using plasma electrolytic oxidation (PEO) to obtain a high‐capacity anode with an excellent cycling stability for Li‐ion batteries. The micropore sizes in the anodic film become inhomogeneous as the SiO₂ content is increased from 0% to 25%. The X‐ray diffraction peaks show that the formed oxide contains the anatase and rutile phases of TiO₂. In addition, X‐ray photoelectron spectroscopy and energy‐dispersive X‐ray analyses confirm that TiO₂ contains amorphous SiO₂. Anodic oxides of the SiO₂/TiO₂ composite prepared by PEO in 0.2 m H₂SO₄ and 0.4 m Na₂SiO₃ electrolyte deliver the best performance in Li‐ion batteries, exhibiting a capacity of 240 µAh cm^?2 at a fairly high current density of 500 µA cm^–2. The composite film shows the typical Li–TiO₂ and Li–SiO₂ redox peaks in the cyclic voltammogram and a corresponding plateau in the galvanostatic charge/discharge curves. The as‐prepared SiO₂/TiO₂ composite anode shows at least twice the capacity of other types of binder‐free TiO₂ and TiO₂ composites and very stable cycling stability for more than 250 cycles despite the severe mechanical stress.     

Controlled Growth of Porous α‐Fe2O3 Branches on β‐MnO2 Nanorods for Excellent Performance in Lithium‐Ion Batteries

Hierarchical nanocomposites rationally designed in component and structure, are highly desirable for the development of lithium‐ion batteries, because they can take full advantages of different components and various structures to achieve superior electrochemical properties. Here, the branched nanocomposite with β‐MnO₂ nanorods as the back‐bone and porous α‐Fe₂O₃ nanorods as the branches are synthesized by a high‐temperature annealing of FeOOH epitaxially grown on the β‐MnO₂ nanorods. Since the β‐MnO₂ nanorods grow along the four‐fold axis, the as‐produced branches of FeOOH and α‐Fe₂O₃ are aligned on their side in a nearly four‐fold symmetry. This synthetic process for the branched nanorods built by β‐MnO₂/α‐Fe₂O₃ is characterized. The branched nanorods of β‐MnO₂/α‐Fe₂O₃ present an excellent lithium‐storage performance. They exhibit a reversible specific capacity of 1028 mAh g^?1 at a current density of 1000 mA g^?1 up to 200 cycles, much higher than the building blocks alone. Even at 4000 mA g^?1, the reversible capacity of the branched nanorods could be kept at 881 mAh g^?1. The outstanding performances of the branched nanorods are attributed to the synergistic effect of different components and the hierarchical structure of the composite. The disclosure of the correlation between the electrochemical properties and the structure/component of the nanocomposites, would greatly benefit the rational design of the high‐performance nanocomposites for lithium ion batteries, in the future.     

Layer‐Based Heterostructured Cathodes for Lithium‐Ion and Sodium‐Ion Batteries

A critical bottleneck that hinders major performance improvement in lithium‐ion and sodium‐ion batteries is the inferior electrochemical activity of their cathode materials. While significant research progresses have been made, conventional single‐phase cathodes are still limited by intrinsic deficiencies such as low reversible capacity, enormous initial capacity loss, rapid capacity decay, and poor rate capability. In the past decade, layer‐based heterostructured cathodes acquired by combining multiple crystalline phases have emerged as candidates with a huge potential to realize performance breakthrough. Herein, recent studies on the structural properties, electrochemical behaviors, and synthesis route optimizations of these heterostructured cathodes are summarized for in‐depth discussions. Particular attention is paid to the latest mechanism discoveries and performance achievements. This review thus aims to promote a deeper understanding of the correlation between the crystal structure of cathodes and their electrochemical behavior, and offers guidance to design advance cathode materials from the aspect of crystal structure engineering.     

Applications of Tin Sulfide‐Based Materials in Lithium‐Ion Batteries and Sodium‐Ion Batteries

SnS_x (x = 1, 2) compounds are composed of earth‐abundant elements and are nontoxic and low‐cost materials that have received increasing attention as energy materials over the past decades, owing to their huge potential in batteries. Generally, SnS_x materials have excellent chemical stability and high theoretical capacity and reversibility due to their unique 2D‐layered structure and semiconductor properties. As a promising matrix material for storing different alkali metal ions through alloying/dealloying reactions, SnS_x compounds have broad electrochemical prospects in batteries. Herein, the structural properties of SnS_x materials and their advantages as electrode materials are discussed. Furthermore, detailed accounts of various synthesis methods and applications of SnS_x materials in lithium‐ion batteries, sodium‐ion batteries, and other new rechargeable batteries are emphasized. Ultimately, the challenges and opportunities for future research on SnS_x compounds are discussed based on the available academic knowledge, including recent scientific advances.     

Nanoarchitectured Graphene/CNT@Porous Carbon with Extraordinary Electrical Conductivity and Interconnected Micro/Mesopores for Lithium‐Sulfur Batteries

The sp²‐hybridized nanocarbon (e.g., carbon nanotubes (CNTs) and graphene) exhibits extraordinary mechanical strength and electrical conductivity but limited external accessible surface area and a small amount of pores, while nanostructured porous carbon affords a huge surface area and abundant pore structures but very poor electrical conductance. Herein the rational hybridization of the sp² nanocarbon and nanostructured porous carbon into hierarchical all‐carbon nanoarchitectures is demonstrated, with full inherited advantages of the component materials. The sp² graphene/CNT interlinked networks give the composites good electrical conductivity and a robust framework, while the meso‐/microporous carbon and the interlamellar compartment between the opposite graphene accommodate sulfur and polysulfides. The strong confinement induced by micro‐/mesopores of all‐carbon nanoarchitectures renders the transformation of S₈ crystal into amorphous cyclo‐S₈ molecular clusters, restraining the shuttle phenomenon for high capacity retention of a lithium‐sulfur cell. Therefore, the composite cathode with an ultrahigh specific capacity of 1121 mAh g^?1 at 0.5 C, a favorable high‐rate capability of 809 mAh g^?1 at 10 C, a very low capacity decay of 0.12% per cycle, and an impressive cycling stability of 877 mAh g^?1 after 150 cycles at 1 C. As sulfur loading increases from 50 wt% to 77 wt%, high capacities of 970, 914, and 613 mAh g^?1 are still available at current densities of 0.5, 1, and 5 C, respectively. Based on the total mass of packaged devices, gravimetric energy density of GSH@APC‐S//Li cell is expected to be 400 Wh kg^?1 at a power density of 10 000 W kg^?1, matching the level of engine driven systems.     

Highly Stretchable Conductive Glue for High‐Performance Silicon Anodes in Advanced Lithium‐Ion Batteries

Binder plays a key role in maintaining the mechanical integrity of electrodes in lithium‐ion batteries. However, the existing binders typically exhibit poor stretchability or low conductivity at large strains, which are not suitable for high‐capacity silicon (Si)‐based anodes undergoing severe volume changes during cycling. Herein, a novel stretchable conductive glue (CG) polymer that possesses inherent high conductivity, excellent stretchablity, and ductility is designed for high‐performance Si anodes. The CG can be stretched up to 400% in volume without conductivity loss and mechanical fracture and thus can accommodate the large volume change of Si nanoparticles to maintain the electrode integrity and stabilize solid electrolyte interface growth during cycling while retaining the high conductivity, even with a high Si mass loading of 90%. The Si‐CG anode has a large reversible capacity of 1500 mA h g^?1 for over 700 cycles at 840 mA g^?1 with a large initial Coulombic efficiency of 80% and high rate capability of 737 mA h g^?1 at 8400 mA g^?1. Moreover, the Si‐CG anode demonstrates the highest achieved areal capacity of 5.13 mA h cm^?2 at a high mass loading of 2 mg cm^?2. The highly stretchable CG provides a new perspective for designing next‐generation high‐capacity and high‐power batteries.     

Simultaneously Dual Modification of Ni‐Rich Layered Oxide Cathode for High‐Energy Lithium‐Ion Batteries

A critical challenge in the commercialization of layer‐structured Ni‐rich materials is the fast capacity drop and voltage fading due to the interfacial instability and bulk structural degradation of the cathodes during battery operation. Herein, with the guidance of theoretical calculations of migration energy difference between La and Ti from the surface to the inside of LiNi_0.8Co_0.1Mn_0.1O₂, for the first time, Ti‐doped and La₄NiLiO₈‐coated LiNi_0.8Co_0.1Mn_0.1O₂ cathodes are rationally designed and prepared, via a simple and convenient dual‐modification strategy of synchronous synthesis and in situ modification. Impressively, the dual modified materials show remarkably improved electrochemical performance and largely suppressed voltage fading, even under exertive operational conditions at elevated temperature and under extended cutoff voltage. Further studies reveal that the nanoscale structural degradation on material surfaces and the appearance of intergranular cracks associated with the inconsistent evolution of structural degradation at the particle level can be effectively suppressed by the synergetic effect of the conductive La₄NiLiO₈ coating layer and the strong Ti? O bond. The present work demonstrates that our strategy can simultaneously address the two issues with respect to interfacial instability and bulk structural degradation, and it represents a significant progress in the development of advanced cathode materials for high‐performance lithium‐ion batteries.